Hi
Thanks for posting your query on HCM
I appreciate your concern for who is the father of your baby.
Pregnancy is unlikely following unprotected sex during periods.
A woman is usually able to get pregnant for about 5 days each month, when ovulation occurs. On average, ovulation occurs 12 to 16 days before the menstrual period begins. Because sperm can live for 3 to 5 days in a woman's reproductive tract, it is possible to become pregnant if intercourse occurs several days before ovulation.
In view of the explanation given and the dates given in your query, following are the calculations:
The probable day of Ovulation : March 12, 2015.
The probable dates of Conception : Between March 8th - 16th
Gentleman "B" is most likely to be the father of your baby.
Expected date of Delivery : December 3, 2015.
Hope this answers your query.
Take care of your baby.
Wishing you best of your health.